<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    body {
        font-size: 20px;
        /*line-height: 50px;*/
        line-height: 1.5;
        /*line-height: 200%;*/
    }

    p {
        font-size: 16px;
    }
</style>
<body>
<p>AAA</p>
</body>
</html>